In the atmosphere, some air molecules can emit electrons under the effect of cosmic rays, ultraviolet light, soil and air radiation in the nature. These electrons combine with neutral molecules in the air and become anion.
Concentration of anion in the air is one of the benchmark of air quality. According to standard laid down by World Health Organization, concentration of negative oxygen ions in fresh air will not be lower than 1,000-1,500 per cubic centimeter. Practically, people have found out that anion is an effective means to kill bacteria, improve air quality and improve health condition. When integrating with bacteria, anion can electrify the bacteria and makes it easier to precipitate and be removed. On the other hand, anion also acts as a reducing agent to react with bacteria, causing bacteria to change its structure or transfer its energy to achieve the effect of sterilization. Study of US Environmental Protection Agency (EPA) laboratory shows that through the Brownian motion in the air, anion can take the initiative to capture dust pellets, makes it agglomerate and precipitate, effectively removing micro dust of 2.5 micrometers (PM2.5) or less, or even 1 micrometer in the air, thereby reducing the hazards of PM2.5 to human health. Study also finds that when the concentration of anion reaches 20,000 per cubic centimeter indoor, the amount of floating dusts in the air will be reduced by more than 98%, in particular, the micro dust, bacteria and viruses of less than 1 micrometer in PM2.5 which cause the most hazards will become almost zero. In addition, anion also has an impact on human body's physiological activities through nervous system and blood circulation. Anion can reinforce the suppress on the human cerebral cortex process to strengthen and adjust the cerebral cortex function, leading to sedative, hypnotic and hypotensive effect; the negative oxygen ion can smoothen and relax the bronchial smooth muscle and relieve its spasm when entering the human respiratory tract; when negative oxygen ion enters blood, it will slow down the sedimentation rate of red blood cell and prolong the clotting time. It can also increase red blood cells and calcium content while reducing white blood cells, calcium and blood sugar. The content of lactic acid in fatigue muscle will also be reduced. Negative oxygen ion can also reinforce the process of oxidation of the body's kidney, liver and brain.
The concentration of anion in the air can be different depending on geographical conditions. Table 1 shows the concentrations of anion in common environments. It can be seen that natural environments such as waterfalls, forests, mountains and coastal area have higher concentration of anion while urban environments such as parks, streets and office have lower anion concentration, even cannot reach the standard of fresh air set by WHO.
TABLE 1Anion Concentration in different environmentsAnion concentration Location(per cubic centimeter)Waterfalls, Forests10,000-20,000Mountains, Coasts 5,000-10,000Parks  400-1,000Streets<200Offices, Vehicles 60-150
Therefore, taking into account the beneficial effects of anion and the reality of lower anion concentration in human living environment, it is desirable to provide means to produce anion artificially. It is more desirable to carry on the means that can produce anion artificially. A preferred means is to manufacture wearable device which can release anion, especially clothing.
There are several methods in the prior art to manufacture wearable device or clothing which can release anion. One of the methods is to produce wearable device or clothing directly using materials that can release anion. CN101513276A discloses the anion silicone rubber made bra. The bra uses silicone rubber as a carrier and mixes it with 0.1% to 3% chemical powder that can generates anion; or produce a pad using silicone rubber and anion chemical powder and insert it into an ordinary bra. Another method is the production of functional fabric that can release anion. CN103643375A discloses a blended anion fiber fabric. The fabric is blended weaved by four kinds of fabric fibers, namely the nanocomposite ceramic fiber, nano-antibacterial wool fibers, nano-bamboo fiber and rayon fiber. These nanofibers accounted for 47-59% of the fabric weight, and are claimed to be capable of releasing anion.
However, there are some defects in the aforementioned methods. Regarding the first method, clothes entirely made with silicone and anion powders are often not comfortable, they are always relatively heavy, and the texture is not as comfortable as fabric. With respect to the second method, the functional component content that can truly release anion tends to be relatively low, resulting in low concentration of anion. The applicant also finds that among the clothes made with these functional fabrics, the anion is mainly generated by friction between the fabrics. In other words, when people are in static environment such as sleeping or working, the functional fabrics release almost no anion.